<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>案例</title>
    <style>
.color{
    background-color: green;
    width:100px;
    height:100px;
}
.div{
   background-color:red ;
    width:100px;
    height:100px;
}
}
    </style>
</head>
<body>
    <div class="div"></div>
    <div class="color"></div>
    <div class="div"></div>
</body>
</html>